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152概率简单数值题short

Expected Draws Until First Birthday Match

题目

People enter a room one at a time, each with a birthday drawn independently and uniformly from 365 days. Let TT be the number of people present when a birthday collision first occurs (i.e., the newcomer shares a birthday with someone already in the room). Write a closed-form expression for E[T]E[T] as a finite sum involving factorials and powers of 365, then approximate it numerically.

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